C++/typename

아래와 같은 소스가 있을때

#include <iostream>
#include <vector>

using std::vector;

template<class T>
class TemplateTest
{
	public:
		TemplateTest() {}
		virtual ~TemplateTest() {}
		void foo(vector<T>& vec)
		{
			vector<T>::iterator it;
			vector<T>::iterator end = vec.end();
			for (it = vec.begin(); it != end; ++it)
			{
			}
		}
};

int main (int argc, char **argv)
{
	return 0;
}

컴파일 하면 아래와 같은 경고가 뜬다.

$ g++ testt.cc
testt.cc: In member function `void TemplateTest<T>::foo(std::vector<T, std::allocator<_CharT> >&)':
testt.cc:14: warning: `std::vector<T, std::allocator<_CharT> >::iterator' is implicitly a typename
testt.cc:14: warning: implicit typename is deprecated, please see the documentation for details
testt.cc:15: warning: `std::vector<T, std::allocator<_CharT> >::iterator' is implicitly a typename
testt.cc:15: warning: implicit typename is deprecated, please see the documentation for details

표준에 따르면

14.6/2 A name used in a template declaration or definition and that is dependent on a template-parameter is assumed not to name a type unless the applicable name lookup finds a type name or the name is qualified by the keyword typename.

즉 위 소스 중에서

vector<T>::iterator it;
vector<T>::iterator end = vec.end();

이 부분을 아래과 같이 수정해야 한다.

typename vector<T>::iterator it;
typename vector<T>::iterator end = vec.end();